The present invention relates to a method of producing a polarisation asymmetric active optical waveguide, a polarisation asymmetric active optical waveguide obtainable by the method; a method of producing a single polarisation mode optical waveguide laser having a pump light source and distributed feedback or distributed Bragg reflector, a single polarisation mode optical waveguide laser having a pump light source and distributed feedback or distributed Bragg reflector obtainable by the method; in particular a multi-wavelength single polarisation mode optical waveguide laser having a pump light source and distributed feedback or distributed Bragg reflector; and uses of such a polarisation asymmetric active optical waveguide and single polarisation mode optical waveguide lasers, in particular in telecommunication networks, in spectroscopy, in sensors, and in absolute calibrated laser light source.